1. Field of the Invention
The present invention relates to a cleaning and drying apparatus for cleaning a wafer to be processed, such as a semiconductor wafer or a glass substrate for LCDs, by immersing the same in a cleaning liquid, and drying the same after cleaning, a wafer processing system, and a wafer processing method.
2. Description of the Related Art
Generally, in a semiconductor device fabricating process to be carried out by a semiconductor device fabricating system, a generally known cleaning method cleans a wafer to be processed (hereinafter referred to simply as "wafer"), such as a semiconductor wafer or a glass substrate for LCDs, by sequentially immersing the wafer in a liquid chemical, a rinsing liquid (cleaning liquid) and such contained in processing tanks. A cleaning system for carrying out such a cleaning method is provided with a drying apparatus which brings a drying gas containing a vapor of a volatile organic solvent, such as isopropyl alcohol, into contact with the surface of the cleaning liquid in order that moisture is removed from the wafer and the wafer is dried by the Marangoni effect. (Refer to JP-A No. 8-148458.)
A conventional cleaning and drying apparatus of this kind includes a cleaning tank storing a cleaning liquid, such as a liquid chemical or a rinsing liquid, having an upper opening covered with a hood (lid). Usually, the lid is made of a strong material, such as polypropylene or a stainless steel, to seal the cleaning tank during a drying process. In this cleaning and drying apparatus, a carrying arm carries a wafer through the open opening into the cleaning tank, transfers the wafer to a wafer supporting means which moves in a transfer unit, and moves out of the cleaning tank. Then, the opening is closed with the lid, the wafer is cleaned in the cleaning tank, and then the wafer is taken out of the cleaning tank for drying.
However, since the wafer is carried into the cleaning tank from above the transfer unit disposed in an upper portion of the cleaning tank, and the wafer is taken out from the cleaning tank after cleaning the wafer by this conventional cleaning and drying apparatus, the carrying arm has a great vertical length (height) and the cleaning and drying apparatus is large. Particularly, there is the trend of change from using 8 in. diameter wafers to using 12 in. diameter wafers for the fabrication of semiconductor devices owing to the progressive miniaturization of semiconductor devices, the advancement of IC complexity to large-scale integration and the progress of mass production in recent years. The use of 12 in. diameter wafers entails the further enlargement of cleaning and drying apparatus and resultant reduction of throughput.
Since the lid and the cleaning tank are made of polypropylene or a stainless steel, particles are liable to be produced, metallic impurities are precipitated or eluted from the lid and the cleaning tank due to aged deterioration. The metallic impurities adhere to wafers to reduce the yield.